From the knowledge that the attachment of galactose residues to pancreatic ribonuclease dimer can direct the enzyme to the liver after intravenous injection, experiments are planned on the cytostatic action of such derivatives toward hepatoma cells in culture and in vivo. The inhibitor of ribonuclease which has been isolated from the human placenta is being used to study its effect in preserving mRNA in in vitro translation systems; the roles of endogenous ribonuclease and inhibitor in tissues such as the placenta are being examined in terms of their possible effects on protein biosynthesis in vivo. The applicability of the method for the isolation of the RNase inhibitor is being applied to beef liver as a possible convenient source of the inhibitor in quantity for use as a laboratory reagent. The 2', 3'-cyclic nucleotide 3'-phosphohydrolase present in major quantity in myelin and spinal cord is being prepared in sufficient amount for chemical characterization and for immunological studies on its distribution. The preparation of a protease-free pancreatic DNase is yielding a stable enzyme which will be cross-lined to RNase for study of the properties of a hybrid enzyme that may act on both strands of a hybrid substrate. Samples of completely ribonuclease-free DNase are being prepared by affinity chromatography for study of their usefulness as reagents in the treatment of nuclei for the isolation of nuclear ribonucleic acids.